I carry the inexpensive CO2 units (with unthreaded cartridges) and a small inexpensive pump (fits in jersey pocket).


As stated, the problems with CO2, in my experience are:
1. Getting the first psi into the tube gently
2. Getting one CO2 cartridge to fill a 25mm tire back to the 90psi minimum I want.


So I use the small inexpensive pump to get the first 10 psi, then the CO2 to fill.
Unthreaded cartridges have many uses and can be purchased in volume for cheap.


2 downsides in my approach - CO2 rig is slightly larger than threaded equivalent, pump is an extra item in my jersey, which is fair for me. When riding with friends, if someone carries a pump, then my jersey is lighter one item.